Boolean Modifier removing parts of my object
From the way you've set up the boolean modifier, I gather you're attempting to stamp a grid pattern into the front of the text, like this?



If that's not the result you're after, then could you clarify what you're trying to achieve?

If that is the desired result, then it's hard to say exactly what is causing the result you're getting without poking around in the .blend.
Since you already tried the two most common culprits, The next general fix I'd try is sticking a remesh modifier on the text (above the boolean modifier). This will generate a new mesh resembling input, hopefully correcting any non-manifold geometry.